Ignition system



07 1934- L. M. PERKINS 1,960,919

IGNITION SYSTEM Filed MarCh l4 1950 Jaurene 777. Per/rims Patented May 29, 1934 UNITED STATES PATENT OFFICE I IGNITION SYSTEM ware Application March 14, 1930, Serial No. 435,783

4 Claims.

This invention relates to a method of and an apparatus for suppressing the disturbances in a radio receiver caused by electromagnetic waves radiated by the ignition system of an internal 5 combustion engine.

The high tension circuit of an internal combustion engine usually comprises a high tension coil having one terminal grounded and the other terminal connected by a conductor to a distributor, leads from the distributor to each of the spark plugs and the return passage for the current from the spark plugs usually through the engine block'and the frame to which the high tension coil is grounded.

According to Principles of Radio Communication by Morecroft 2nd edition, page 356 the transmitting antenna must have a large volume displacement. This indicates that the larger the volume of the loop enclosed by the antenna the greater will be the radiation from the antenna. As this is the case, the reduction of the volume enclosed by the loop of the circuit certainly will reduce the radiation of disturbing electromagnetic waves.

An object of this invention is to reduce the loop of the high tension circuit to a minimum. This has been accomplished by providing an auxiliary circuit comprising a return circuit which is immediately adjacent to the circuit from 30 the high tension coil to the spark plugs.

Another object of this invention is to provide a. return circuit having both ends grounded.

This has been accomplished by enclosing the grounded wire in a ferro-magnetic shield which 35 also encloses the circuit from the high tension coil to the spark plug. By this construction a current is generated or induced in the return lead which will flow in the opposite direction from the current passing from the high tension 40 coil to the spark plug.

Another object of this invention is to completely shield the entire high tension circuit so that any disturbances radiated by the small loop of the high tension circuit will not cause any disturbances in a nearby radio.

Further objects and advantages'of the present invention will be apparent from the following description, reference being had to the accompanying drawing, wherein a preferred embodiment of one form of the present invention is clearly shown.

In the drawing:

' Fig. 1 discloses a schematic diagram of the high tension circuit.

Fig. 2'shows a schematic diagram of part of the high tension circuit and four cylinders of the engine in side elevation. The balance of the circuit in Fig. 2 has been omitted for the sake of clearness.

In the drawing the reference character 10 indicates a low tension coil of an ignition system energized from a source of E. M. F. 12 a storge battery and an interrupter 14 mounted within a metallic casing 15. Mounted within the metal.-

lic casing 16 and concentric with the low tension coil 10 is found the high tension coil 18 having one terminal 20 grounded to the casing 16 which is grounded at 22 and the other terminal 24 connected to the distributor 26 by a lead 27.

In Fig. 1 an eight cylinder engine has been shown. The contacts 28, 30, 32 and 34 are connected to the spark plugs 36, 38, 40 and 42 by the leads 44, 46, 48 and 50. The contacts 52, 54, 56 and. 58 are connected to the other set of spark plugs 60, 62, 64 and 66 by the leads 68, 70, '72 and 74.

The auxiliary circuit or the return circuit from the cylinder to the right as viewed in Fig. 1 includes the conductor '76. grounded at 78 to the engine or cylinder block and joined to a conductor 80 at 82, the conduct-or 80 being grounded at 84 to the metallic casing 16. Grounded as here used and as used in the claims designates an electrical connection to a metallic conductor without necessarily being .connected to earth. The return lead for the left cylinder block includes a conductor 86 grounded to the block at 88 and joined to the grounded lead 80 at 82. The leads 27 and 80 have been enclosed in a metallic shield 90 which extends a greater portion of distance from the metallic casing 16 to a metallic shield 96 which encloses the distributor and the balance of the leads 27 and 80. The leads 44, 48, 50 and 76 have been enclosed in a" metallic shield 94 and the spark plugs 36, 38, 40 and 42 have been enclosed in a metallic shield 92. The leads 68, 70, 72 and '74 and the return lead 86 leading to the right cylinder block have been enclosed in a metallic shield 98 and the spark plugs 60, 62, 64 and 66 in a metallic shield 100. All of these shields have been grounded as indicated 'by the reference character 9.

Whenever the distributor 26 engages with one of the contacts 28, 30 etc., the circuit through the high tension coil 18, the lead 27, the distributor 26, the particular contacts as 28, 30 etc., and the lead extending from the particular contact to its spark plug which is grounded to the block is closed. Whenever this circuit is closed a current flows through this circuit, first accumulating on flow thereby,

the electrodes of the spark plug and then flashing across these electrodes forming the are used for igniting the compressed charge in the cylinder, which is well known tothose skilled in the art. When this takes place the magnetic lines of force which pass in the shields 90, 92, 94 or 98, as the case may be, will in turn generate or induce an E. M. F. in the opposite direction'in the lead and either lead '76 or 86, as the case may be. This generated or induced E. M. F. causes a current to forming a return circuit for the current so that practically no current will flow through the frame and the block of the engine. This reduces the loop to a minimum.

It may seem 01f hand, that the current induced in the lead 80 would divide, part flowing through the conductor 76 and part through 86. This however, is not the case for the reason that when a current flows through one of the spark plugs in the right cylinder block, magnetic lines of force will be set up in the shield 94, thereby generating an E. M. F. in the conductor 76 which will cause most of the current flowing through the conductor 80 to continue through the conductor 76, likewise, when the distributor closes the circuit to one of the spark plugs on the left cylinder block magnetic lines of force will pass through the ferromagnetic shield 98 which causes an E. M. F. to be generated in the conductor 86 so that this conductor will carry most of the current flowing through the conductor 80.

It can be readily seen that this system provides an auxiliary orreturn lead for each of the cylinder'blocks, each of said return leads having the lead 80 in common. Although the drawings disclose the device applied to an eight cylinder vtype engine or a twin-four, it can be used with other types of engines within the purview of this invention.

Instead of having a plurality of shields, the entire circuit could be enclosed in a common shield.

In some cases it may be desirable to provide a grounded lead for the return of the current in the low tension circuit.. This may be accomplished by providing a return lead 102 having one terminal 104 grounded on the casing 16 and the other terminal 106 grounded to the negative terminal 108 on the battery. This together with the lead 110 connecting the low tension coil 10 to the battery is enclosed in a ferro-magnetic shield 15 which causes a current to flow in the return lead 102 which flows in the opposite direction to the current in the lead 110.

While the form of embodiment'of the present invention as herein disclosed, constitutes a preferred form, it is to be: understood that other forms might be adopted, all coming within the scope of the claims which follow.

What is claimed is as follows:

plug circuit of said ignition system, said leads passing adjacent to each other so that a high frequency current-impulse in the first lead will generate a substantially equal and opposite current impulse in the other lead.

2. In combination in an engine ignition system, a high tension induction coil having primary and secondary windings, means for energizing said primary winding, a ground connection to the low potential end of said secondary winding, one or more spark plugs grounded to the engine block, a conductive connection between the highpotential end of said secondary winding and said plug, and a return conductor having one end grounded to the engine block near said spark plug and its opposite end grounded near'said induction coil, said conductive connection and said return conductor being arranged adjacent to each .other so that high frequency waves radiated by one will be substantially neutralized by similar waves of opposite phase radiated by the other.

3. The structure defined in claim 2 in combination with a shield formed of ferro-magnetic material enclosing said conductive connection and said return conductor.

4. In combination in an engine ignition sysopposite end to one of said spark plugs, a return lead having one end grounded to the cylinder block near the spark plugs and its other end rounded near the induction coil, said return lead being arranged closely adjacent to the conductors running to the spark plugs, shielding means enclosing said return lead and said plurality of conductors, and a grounded shield enclosing the exposed portions of said spark plugs.

LAURENCE M. PERKINS. 

